Textarea element goes over the top of z-index 1 navigation bar

[WebCoder49]

Reproduced in Firefox 140.0.2-1.
The code-input has CSS z-index of 0, and the navigation bar is defined before the code-input and has z-index of 1.

This makes clicking on the navigation bar select text in the code-input element rather than interact with the navigation bar.

This is unexpected to a user of code-input, who doesn't know its inner workings. Everything in the code-input should be below all greater z-index layers of elements outside, or if this bug is unfixable it should be documented.